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July 14, 2026 — Susan Greene

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As scientists monitor a developing El Niño event in the Pacific, a provocative question has moved from science fiction closer to scientific debate:

Could humans intentionally modify Earth’s climate to reduce the impacts of extreme weather?

The research was partly inspired by an unexpected natural experiment: the massive Australian wildfires of 2019–2020. Smoke particles from the fires traveled across the Pacific and altered cloud properties, providing researchers with additional information about how aerosols can influence clouds and climate patterns.

A recent modeling study investigated whether targeted marine cloud brightening could reduce the intensity of extreme El Niño events. Researchers simulated cloud brightening in the southeastern Pacific during historical events, including the powerful 1997–1998 and 2015–2016 El Niños. Their models suggested that targeted intervention could weaken some El Niño impacts by cooling ocean surfaces and influencing atmospheric circulation.

However, the study does not mean scientists have developed an El Niño “off switch.” It is a computer modeling study, not a recommendation for immediate deployment.

The climate system is connected—changing one piece can affect many others

While some research explores whether marine cloud brightening could reduce extreme El Niño events, other research raises a different concern:

ENSO is not simply a source of disruptive weather. It is a natural climate rhythm that influences ecosystems, ocean productivity, and global weather patterns.

A 2025 study in Earth’s Future examined long-term marine cloud brightening over the subtropical eastern Pacific. Researchers found that sustained MCB in this region could substantially suppress ENSO variability, reducing the strength of El Niño and La Niña cycles in climate model simulations.

This finding highlights an important distinction: reducing an extreme climate event is not the same as restoring a natural climate system.

The challenge is that Earth’s climate system contains many interconnected feedbacks. A change designed to solve one problem may create changes elsewhere.

Aerosols: Could climate engineering create new pollution concerns?

The word aerosol often carries negative associations because many human-produced aerosols—such as industrial particulate pollution—are harmful to human health.

However, not all aerosols are alike.

Marine cloud brightening would likely use sea-salt particles, which are chemically different from pollutants such as sulfate particles produced by fossil fuel combustion. Current research does not suggest that sea-salt aerosols would create the same respiratory risks associated with industrial air pollution.

However, large-scale deployment has never occurred, leaving unanswered questions:

• How would continuous aerosol release affect marine ecosystems?
• Could particles influence coastal air quality?
• How would cloud chemistry change over decades?
• Could regional climate responses differ from model predictions?

Researchers emphasize that major scientific gaps remain in understanding aerosol behavior, cloud responses, and possible unintended effects.

Other forms of solar geoengineering create different concerns. Stratospheric aerosol injection (SAI), which would place reflective particles high in the atmosphere, has raised questions about atmospheric chemistry, including possible effects on ozone. Research into solar geoengineering continues to examine these potential interactions.

Human health: What do we know?

Climate intervention research intersects with public health in two ways.

First, climate change itself creates health risks through: heat exposure, wildfire smoke, extreme weather, food insecurity, and disease expansion.

Second, any deliberate atmospheric intervention must consider possible unintended effects.

Fine particulate matter, especially PM2.5, is strongly associated with respiratory and cardiovascular disease. Organizations including the World Health Organization and the U.S. Environmental Protection Agency have documented these risks.

Marine cloud brightening differs from pollution because the proposed particles are primarily sea salt rather than combustion-derived particles. However, scientists stress that long-term atmospheric manipulation has never been tested at planetary scales.

The biggest limitation: Geoengineering does not solve climate change

Perhaps the most important point is that solar geoengineering does not remove greenhouse gases.

The National Academies of Sciences, Engineering, and Medicine concluded that solar geoengineering research should continue cautiously, with strong governance and transparency, while emphasizing that it cannot replace emissions reductions.

The IPCC similarly identifies reducing greenhouse gas emissions, protecting natural carbon sinks, adaptation, and carbon removal as essential strategies for addressing climate change.

The risk of dependence: What happens if we stop?

One concern frequently discussed in geoengineering research is termination shock.

If solar geoengineering temporarily masks warming while greenhouse gases continue accumulating, suddenly ending the intervention could result in rapid warming because the underlying climate forcing would still exist.

This possibility is one reason many researchers argue that geoengineering must never become a substitute for reducing emissions.

The question is not only “Can we?”

Humanity is approaching a point where we may have the technological ability to intentionally influence parts of Earth’s climate system.

The more difficult question is: should we?

Climate engineering raises questions that science alone cannot answer:

• Who decides when deployment occurs?
• Who benefits?
• Who bears the risks?
• How do we respond if different regions experience different outcomes?
• Can a technology designed to stabilize climate create new vulnerabilities?

The newest research does not provide a simple answer. Instead, it highlights something scientists have long understood:

Earth’s climate is a connected system.

Clouds, oceans, atmosphere, ecosystems, and human societies are intertwined. Before attempting to modify one part of that system, we must understand the consequences throughout the whole.

The ability to influence the climate would be one of humanity’s greatest technological achievements—but using that ability responsibly may be an even greater challenge.